The inventive concept relates to semiconductor devices and to methods of fabricating the same. In particular, the inventive concept relates to halo implantation processes used in the fabricating of semiconductor devices.
The rapid growth of electronic products that process information, such as computers, has brought about a rapid progress in the development of semiconductor devices such as semiconductor memories. These developments include increases in the integration of the devices aimed at reducing the cost of the devices without compromising their quality. Realizing a high degree of integration of semiconductor devices requires a scaling-down of existing devices, e.g., minimizing the thickness of gate oxide films of the transistors of semiconductor devices and of the channel lengths of the transistors. These reductions may result in or be accompanied by reductions in the spacing between the transistors, and in the widths of the gate regions of the transistors.
However, in these respects, electrical properties of a transistor are considerably affected by a critical dimension (CD) of its gate region. For instance, as the width of the gate region of the transistor(s) of a semiconductor device becomes smaller to increase the degree of integration of the device, the distance between the source and drain regions of the transistor also becomes smaller. This distance may correspond to the effective length of the channel through which charge carriers (electrons or holes) move when the transistor is in a certain state. However, when the effective channel length of a transistor is relatively small, so-called short channel effects can occur.
Various methods have been considered for suppressing short channel effects. One of these methods is a halo implantation process of implanting a high concentration of ions into a substrate in forming the source and drain regions of a transistor.
However, as semiconductor devices become more highly integrated and the critical dimension (CD) of a gate region decreases to meet the smaller design rules for the devices, the ions implanted during the halo ion implantation process may tend to diffuse into a channel region of a transistor, thereby negatively impacting the performance of the transistor by, for example, increasing the threshold voltage (Vth) distribution of the transistor or reducing the mobility of the charge carriers in the channel region.